The recently approved FASERnu detector is the first neutrino experiment at the LHC. It will detect over thousands of neutrino interactions during the upcoming Run 3 of the LHC, with typical neutrino energies of a TeV. It will measure neutrino cross sections at energies where they are currently unconstrained, will bound models of forward particle production, and could open a new window on physics beyond the standard model. As the first of its kind, FASERnu also paves the way for a high energy neutrino frontier program during the HL-LHC era, with higher luminosities and possibly larger detectors. We propose to explore the full SM and BSM physics potential of collider neutrino experiments at the LHC and future colliders, and look forward to many great ideas from the energy frontier community.